Recently, as distribution of smart phones, and tablet PCs, IPTVs, and the like has accelerated, requirement for a touch function in which a hand of human directly becomes an input device without a separate input device such as a keyboard or a remote controller has gradually increased. Further, a writable multi-touch function has been additionally required in addition to a specific point touch function.
The touch panel having the functions may be classified as follows according to a signal detecting method.
That is, the touch panels are divided into a resistive type detecting a position pressed by a pressure through a change in a current or voltage value in a state where DC voltage is applied, a capacitive type using capacitance coupling in a state where AC voltage is applied, and an electromagnetic type detecting a selected position as a change in voltage in a state where a magnetic field is applied.
Among the types, the most common resistive type and capacitive type touch panels recognize a touch or not according to an electrical touch or a change of capacitance by using a transparent conductive film such as an ITO film. However, the transparent conductive film almost has high resistance of 150 ohm/square or more, and sensitivity when increasing a size deteriorates. In addition, as a size of a screen is increased, costs of the ITO film increase, and as a result, commercialization is not easy. In order to solve the problem, an attempt to implement a large size by using a metal pattern having high conductivity has been performed.
When the touch panel is formed by the metal pattern, a minute pattern is provided on a screen part, while a conductive pattern needs to be provided in a relatively wide region of a pad part for connection with a power source. Accordingly, in the case of using a photolithography method in order to form the screen part and the pad part at once, a lot of costs are consumed, and in the case of using a printing method, a pattern having a desired shape is not formed due to a touch of a print roll on the bottom. In order to overcome the problem, a method of forming the screen part and the pad part by different processes has been attempted, but there is a problem in that the processes are complicated and a lot of costs are consumed.